Genetic heterogeneity of deafness phenotypes linked to DFNA4

Mutations in the heavy chain of the class II nonmuscle myosin, MYH14, cause autosomal dominant hearing loss in families linked to the DFNA4 locus. Consistent with this discovery, we identified an S120L mutation in MYH14 in a large German family segregating deafness that links to DFNA4. However, complete screening of the American family that originally defined the DFNA4 locus revealed no mutations in this gene. Furthermore, haplotyping of a single nucleotide polymorphism (SNP) 5' to MYH14 excludes this gene from the critical region in this family. Our results imply that mutations in another gene result in deafness at the DFNA4 locus. The newly defined candidate region encompasses a region of approximately 19 cM. Several candidate genes have been screened for disease-causing mutations.